Microwave adaptors and related oscillator systems

ABSTRACT

An adaptor for a solid-state oscillator and related microwave adaptors includes an input segment of a conductive material, a first coaxial portion that includes a first inner conductor coupled to the input segment and a first outer shielding segment, and a capping portion coupled to the first coaxial portion to electrically couple the first inner conductor and the first outer shielding segment.

BACKGROUND OF THE INVENTION

The present invention is related generally to electronic circuits, andmore particularly, to microwave adaptors for solid-state microwaveoscillators.

Magnetrons are commonly used to generate microwaves in microwave ovensand other microwave applications. While magnetrons are well suited foruse in microwave ovens, they typically require a relatively high voltagepower source (e.g., 4 kilovolts or more) for operation. Additionally,the lifetime of some magnetrons may be limited or the magnetrons mayotherwise be susceptible to output power degradation over extendedperiods of operation. Accordingly, it is desirable to providealternative sources for microwave energy.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the subject matter may be derived byreferring to the detailed description and claims when considered inconjunction with the following figures, wherein like reference numbersrefer to similar elements throughout the figures.

FIG. 1 is a schematic block diagram of an exemplary oscillator system inaccordance with one embodiment of the invention;

FIG. 2 is a top view of exemplary resonant circuitry suitable for use inthe oscillator system of FIG. 1 in accordance with one embodiment of theinvention;

FIG. 3 is a cross-sectional view of an exemplary adaptor suitable foruse in the oscillator system of FIG. 1 in accordance with one embodimentof the invention; and

FIG. 4 is a schematic circuit diagram of an equivalent circuit for oneembodiment of the adaptor of FIG. 3 that is suitable for use in theoscillator system of FIG. 1.

DETAILED DESCRIPTION

The following detailed description is merely illustrative in nature andis not intended to limit the embodiments of the subject matter or theapplication and uses of such embodiments. As used herein, the word“exemplary” means “serving as an example, instance, or illustration.”Any implementation described herein as exemplary is not necessarily tobe construed as preferred or advantageous over other implementations.Furthermore, there is no intention to be bound by any expressed orimplied theory presented in the preceding technical field, background,or the following detailed description.

Embodiments of the subject matter described herein relate to solid-stateoscillator systems and related adaptors for microwave applications. Asdescribed in greater detail below, exemplary oscillator systems arerealized using an amplifier arrangement with a resonant circuit in thefeedback path. The resonant circuit includes a pair of arcuate (orcurved) inductive elements that oppose one another to provide an annularstructure. As used herein, an “annular structure” should be understoodas referring to a ring-like structure that has a voided interior, butthe annular structure need not be perfectly circular. In exemplaryembodiments, the arcuate inductive elements have substantially identicaland complementary shape and/or dimensions and are capacitively coupledto each other at their opposing ends. In accordance with one or moreembodiments, a rectangular inductive element is formed proximate one ofthe arcuate inductive elements and spaced apart from the respectivearcuate inductive element such that rectangular inductive element iscapacitively coupled to the arcuate inductive element via the gapcapacitance introduced by the air gap between the rectangular inductiveelement and the arcuate inductive element.

For microwave ovens and related applications, to transfer the output ofthe oscillator system to a waveguide and/or cavity, an adaptor isprovided at the output of the oscillator system that translates theoscillating electrical signals from the output impedance of theamplifier arrangement to the input impedance of the waveguide and/orcavity. As described in greater detail below, an exemplary adaptorincludes an input segment of a conductive material, such as a microstriptransmission line, that is coupled to the output of the oscillatorsystem. The adaptor also includes one or more coaxial portionsconfigured to translate the oscillating electrical signals at the outputof the oscillator system to the input impedance of the waveguide and/orcavity, and an antenna portion at the end of the one or more coaxialportions. At least the antenna portion is disposed within the waveguideand/or cavity, and the antenna portion electrically couples the innerconductor to the outer shielding segment of the last coaxial portion toradiate electromagnetic signals (or waves) corresponding to theoscillating signals generated by the oscillator system into thewaveguide and/or cavity. Although the subject matter is described hereinin the context of microwave ovens or other microwave frequencyapplications, the subject matter is not intended to be limited to anyparticular frequency range.

Turning now to FIG. 1, in an exemplary embodiment, an oscillator system100 suitable for use in a microwave oven 150 includes, withoutlimitation, an oscillator arrangement 102, frequency tuning circuitry104, bias circuitry 106, a microwave adaptor 108, and a waveguide 110.In an exemplary embodiment, the elements of the oscillator system 100are configured to produce an oscillating electromagnetic signal at theinput of the waveguide 110 having a frequency in the microwave frequencyrange (e.g., 2.45 GHz) with an output power of about 100 Watts or more.It should be understood that FIG. 1 is a simplified representation of anoscillator system 100 for purposes of explanation and ease ofdescription, and that practical embodiments may include other devicesand components to provide additional functions and features, and/or theoscillator system 100 may be part of a much larger electrical system, aswill be understood.

In an exemplary embodiment, the oscillator arrangement 102 includes anamplifier arrangement 120, resonant circuitry 122, amplifier inputimpedance matching circuitry 124, and amplifier output impedancematching circuitry 126. The resonant circuitry 122 is coupled betweenthe output node 116 of the amplifier arrangement 120 and the input node114 of the amplifier arrangement 120 to provide a resonant feedback loopthat causes the amplified electrical signals produced by the amplifierarrangement 120 to oscillate at or near the resonant frequency of theresonant circuitry 122. As described in greater detail below, in anexemplary embodiment, the resonant circuitry 122 is configured toprovide a resonant frequency of 2.45 GHz, or in other words, theresonant circuitry 122 resonates at 2.45 GHz such that the amplifiedelectrical signals produced by the amplifier arrangement 120 at theamplifier output 116 oscillate at or near 2.45 GHz. It should be notedthat in practice, embodiments of the resonant circuitry 122 may beconfigured to resonate a different frequency to suit the needs of theparticular application utilizing the oscillator system 100.

In exemplary embodiments, the amplifier arrangement 120 is realized asone or more transistors having an input terminal (or control terminal)coupled to the amplifier input node 114 and an output terminal coupledto the amplifier output node 116. In the illustrated embodiment, theamplifier arrangement 120 includes a transistor 130 realized as anN-type field effect transistor (FET) having a gate terminal connected tothe amplifier input node 114, a drain terminal connected to theamplifier output node 116, and a source terminal connected to a node 142configured to receive a ground reference voltage for the oscillatorsystem 100. In an exemplary embodiment, the transistor 130 is realizedas a laterally diffused metal oxide semiconductor (LDMOS) transistor.However, it should be noted that the transistor 130 is not intended tobe limited to any particular semiconductor technology, and in otherembodiments, the transistor 130 may be realized as a gallium nitride(GaN) transistor, a MOSFET transistor, a bipolar junction transistor(BJT), or a transistor utilizing another semiconductor technology.Additionally, in other embodiments, the amplifier arrangement 120 may berealized using any suitable amplifier topology and/or the amplifierarrangement 120 may include multiple transistors.

In an exemplary embodiment, the frequency tuning circuitry 104 generallyrepresents the capacitive elements, inductive elements, and/or resistiveelements that are configured to adjust the oscillating frequency of theoscillating electrical signals generated by the oscillator system 100.In an exemplary embodiment, the frequency tuning circuitry 104 iscoupled between the ground reference voltage node 142 and the input node112 of the oscillator arrangement 102. The bias circuitry 106 generallyrepresents the circuit elements, components, and/or other hardware thatare coupled between the amplifier arrangement 120 and a node 140configured to receive a positive (or supply) reference voltage. Inexemplary embodiments, the voltage difference between the supply voltagenode 140 and the ground voltage node 142 is less than 50 Volts. The biascircuitry 106 is configured to control the direct current (DC) ornominal bias voltages at the gate and drain terminals of the transistor130 to turn the transistor 130 on and maintain the transistor 130operating in the saturation (or active) mode during operation of theoscillator system 100. In this regard, the bias circuitry 106 is coupledto the gate terminal of the transistor 130 of the amplifier arrangement120 at the amplifier input node 114 and the drain terminal of thetransistor 130 at the amplifier output node 116. In accordance with oneor more embodiments, the bias circuitry 106 includes temperaturecompensation circuitry configured to sense or otherwise detect thetemperature of the transistor 130 and adjust the gate bias voltage atthe amplifier input node 114 in response to increases and/or decreasesin the temperature of the transistor 130 to maintain substantiallyconstant quiescent current for the transistor 130 in response totemperature variations.

As illustrated, the oscillator arrangement 102 includes amplifier inputimpedance matching circuitry 124 coupled between the resonant circuitry122 at the input node 112 of the oscillator arrangement 102 and theamplifier input 114, wherein the impedance matching circuitry 124 isconfigured to match the input impedance of the amplifier arrangement 120at the amplifier input node 114 to the impedance of the resonantcircuitry 122 and the frequency tuning circuitry 104 at node 112 at theresonant frequency of the resonant circuitry 122. Similarly, theamplifier output impedance matching circuitry 126 is coupled between theamplifier output 116 and the resonant circuitry 122 to match the outputimpedance of the amplifier arrangement 120 at the amplifier output node116 to the impedance of the resonant circuitry 122 at the output node118 of the oscillator arrangement 102 at the resonant frequency.

In an exemplary embodiment, the microwave adaptor 108 is realized as amicrostrip-to-waveguide adaptor that is coupled between output node 118of the oscillator arrangement 102 and the input of the waveguide 110 totranslate oscillating electrical signals at the output node 118 toelectromagnetic signals (or waves) at the oscillating frequency that areprovided to the input of the waveguide 110. In exemplary embodiments,the microwave adaptor 108 is configured to match the input impedance ofthe waveguide 110 to the impedance at the oscillator output node 118 atthe resonant frequency. For example, in one embodiment, the inputimpedance of the waveguide 110 is about 300 ohms and the impedance atthe oscillator output node 118 is approximately 50 ohms, wherein themicrowave adaptor 108 translates the oscillating electrical signals atapproximately 50 ohm impedance to oscillating electrical signals atapproximately 300 ohm impedance. In exemplary embodiments, the microwaveadaptor 108 includes an antenna portion disposed within the waveguide110 at or near the input of the waveguide 110, wherein the antennaportion translates the oscillating electrical signals at the 300 ohmimpedance to corresponding electromagnetic signals (or waves) at theoscillating frequency that are radiated into or otherwise provided tothe input of the waveguide 110. For example, in a microwave ovenapplication where the resonant circuitry 122 is configured to provide aresonant frequency of 2.45 GHz, the microwave adaptor 108 translates theoscillating electrical signals at the oscillator output node 118 toradiated microwave electromagnetic signals at 2.45 GHz provided to theinput of the waveguide 110, wherein the waveguide 110 directs themicrowave signals into the cavity (or cooking chamber) of the microwaveoven 150.

FIG. 2 depicts an exemplary embodiment of a resonant circuit 200suitable for use as the resonant circuitry 122 in the oscillator system100 of FIG. 1. The resonant circuit 200 includes an annular resonancestructure 202 and a pair of inductive elements 204, 206. The annularresonance structure 202 includes a pair of arcuate (or curved) inductiveelements 208, 210 that are capacitively coupled at their longitudinalends 212, 214. The arcuate inductive elements 208, 210 are substantiallyidentical and complementary in shape, such that the arcuate inductiveelements 208, 210 provide a symmetrical annular structure 202 having avoided interior region 203 when their longitudinal ends 212, 214 face orotherwise oppose those of the other arcuate inductive element 208, 210,as illustrated in FIG. 2. To put it another way, the arcuate inductiveelements 208, 210 are curved inward towards one another to provide asymmetrical annular structure 202 that encompasses a voided interiorregion 203. By virtue of the inductive elements 208, 210 beingsubstantially identical in shape, the inductive elements 208, 210 havesubstantially identical electrical characteristics to provide arelatively high quality factor (or Q value) for the resonant circuit200. In the illustrated embodiment, the arcuate inductive elements 208,210 are substantially U-shaped such that the annular resonance structure202 is substantially rectangular with rounded corners, however, in otherembodiments, the arcuate inductive elements 208, 210 may substantiallyC-shaped such that the annular resonance structure 202 is substantiallycircular. In this regard, the overall shape of the annular resonancestructure 202 may vary depending on area or layout requirements or otherdesign constraints for a particular embodiment. In an exemplaryembodiment, the inductive elements 208, 210 are each realized as amicrostrip or another conductive material (e.g., a conductive metaltrace) formed on an electrical substrate 201, such as a printed circuitboard. The physical dimensions of the inductive elements 208, 210 arechosen to provide a desired inductance such that the annular resonancestructure 202 resonates at a desired frequency. For example, the lengthand width of the inductive elements 208, 210 may be chosen such that theannular resonance structure 202 resonates at a frequency of about 2.45GHz. In accordance with one embodiment, to provide a resonant frequencyof about 2.45 GHz with a conductive metal material (or microstrip)having a thickness of about 0.0024 inches, the length 240 of eachinductive element 208, 210 in a first direction is about 1.03 inches,the length 250 of each inductive element 208, 210 in a second directionorthogonal to the first direction is about 0.42 inches, and the width260 of each inductive element 208, 210 is about 0.058 inches with aninner radius 270 of about 0.121 inches, wherein the width of the airgaps 216, 218 between the ends of the inductive elements 208, 210 isabout 0.02 inches.

As illustrated in FIG. 2, the longitudinal ends 212, 214 of the arcuateinductive elements 208, 210 are spaced apart from one another orotherwise separated to provide air gaps 216, 218 between thelongitudinal ends 212, 214 of the inductive elements 208, 210. In theillustrated embodiment, the resonant circuit 200 includes a pair ofcapacitive elements 220, 222 coupled electrically in series between theinductive elements 208, 210. In an exemplary embodiment, each capacitiveelement 220, 222 is realized as a capacitor, such as a multilayerceramic chip capacitor, that is mounted across the air gaps 216, 218between the longitudinal ends 212, 214 of the inductive elements 208,210 to provide a substantially continuous annular structure. In thisregard, each capacitive element 220, 222 has a first terminal that ismounted, affixed, or otherwise connected to an end 212 of the firstarcuate inductive element 208 and a second terminal that is mounted,affixed, or otherwise connected to the opposing end 214 of the secondarcuate inductive element 210. In this manner, the capacitive elements220, 222 are connected electrically in series between the inductiveelements 208, 210. In an exemplary embodiment, the capacitances of thecapacitive elements 220, 222 are substantially identical and chosenbased on the inductances of the inductive elements 208, 210 such thatthe resonant circuit 200 resonates at a desired frequency. For example,in an exemplary embodiment, the capacitance of the capacitive elements220, 222 is chosen such that the resonant circuit 200 resonates at afrequency of about 2.45 GHz. In an exemplary embodiment, the capacitanceof the capacitive elements 220, 222 is about 2.2 picofarads.

It should be noted that in accordance with one or more alternativeembodiments, the resonant circuit 200 may not include capacitiveelements 220, 222. In this regard, the capacitive coupling provided bythe air gaps 216, 218 between the ends 212, 214 of the inductiveelements 208, 210 may provide the desired capacitance such that theresonant circuit 200 resonates at the desired frequency. For example,the physical dimensions and/or shape of the inductive elements 208, 210may be chosen to provide a desired inductance and the size of the airgaps 216, 218 (i.e., the separation distance between ends 212, 214) maybe chosen to provide a desired capacitance (for example, 2.2 picofarads)such that the resonant circuit 200 resonates at the desired resonantfrequency without capacitive elements 220, 222.

Still referring to FIG. 2, the inductive elements 204, 206 generallyrepresent the input and output terminals of the resonant circuit 200.For convenience, but without limitation, the first inductive element 204may alternatively be referred to herein as the input inductive elementand the second inductive element 206 may alternatively be referred toherein as the output inductive element. As described in greater detailbelow with reference to FIG. 1, in exemplary embodiments, the inputinductive element 204 is coupled to the output node 118 of theoscillator arrangement 102 and the output inductive element 206 iscoupled to the input node 112 of the oscillator arrangement 102.

In the illustrated embodiment of FIG. 2, the input inductive element 204is realized as a rectangular microstrip (or another conductive material)formed on the electrical substrate 201 proximate the first arcuateinductive element 208. The input inductive element 204 is spaced apartor otherwise separated from the inductive element 208 by an air gap 224that functions as a gap capacitor electrically in series between theinductive elements 204, 208. In this regard, the input inductive element204 is capacitively coupled to the inductive element 208 via the gapcapacitance provided by the air gap 224. In an exemplary embodiment, theseparation distance between the inductive elements 204, 208 (e.g., thewidth of the air gap 224) is chosen to be as small as possible toincrease the quality factor (or Q value) of the gap capacitance. Inaccordance with one embodiment, the separation distance between theinductive elements 204, 208 is about 0.01 inches or less.

In a similar manner, the output inductive element 206 is realized asanother rectangular microstrip (or another conductive material) formedon the electrical substrate 201 proximate the second arcuate inductiveelement 210. In the illustrated embodiment, the output inductive element206 is spaced apart or otherwise separated from the inductive element210 by an air gap 226 that functions as a gap capacitor between theinductive elements 206, 210 in a similar manner as described above withrespect to air gap 224. The inductive elements 204, 206 aresubstantially rectangular in shape, and the dimensions of the respectiveinductive elements 204, 206 are chosen to provide a desired input and/oroutput impedance for the resonant circuit 200 at the resonant frequencyof the resonant circuit 200, as described in greater detail below. Itshould be noted that although FIG. 2 depicts air gaps 224, 226 betweenthe both of the inductive elements 204, 206, in accordance with one ormore alternative embodiments, one of the inductive elements 204, 206 maybe electrically connected to the annular resonance structure 202 withouta series capacitance. For example, in accordance with one embodiment,the output inductive element 206 may be formed to physically contact theannular resonance structure 202 and/or arcuate inductive element 210. Inthis regard, the inductive element 206 may be integrally formed with thearcuate inductive element 210 of the annular resonance structure 202. Inan exemplary embodiments, at least one of the inductive elements 204,206 is separated from the annular resonance structure 202 by an air gap224, 226 to increase the quality factor (or Q value) of the resonantcircuit 200. In an exemplary embodiment, the quality factor (or Q value)of the resonant circuit 200 is about 190 or more.

Fabrication of the resonant circuit 200 may be achieved by forming theinductive elements 204, 206, 208, 210 on the electrical substrate 201and forming capacitive elements 220, 222 coupled between thelongitudinal ends 212, 214 of the arcuate inductive elements 208, 210.In this regard, the fabrication process may begin by forming a layer ofconductive material overlying the electrical substrate 201 andselectively removing portions of the conductive material to provide thearcuate inductive elements 208, 210 that define the annular resonancestructure 202 having the voided interior region 203 (e.g., an exposedregion of the electrical substrate 201 substantially encompassed by thearcuate inductive elements 208, 210) and the inductive elements 204, 206proximate the arcuate inductive elements 208, 210. As described above,portions of the conductive material between at least one of theinductive elements 204, 206 and a respective arcuate inductive element208, 210 are removed to provided a gap capacitance in series betweenthat respective inductive element 204, 206 and the respective arcuateinductive element 208, 210 proximate the respective inductive element204, 206. Additionally, portions of the conductive material are removedto provide air gaps 216, 218 between the longitudinal ends 212, 214 ofthe arcuate inductive elements 208, 210. After forming the inductiveelements 204, 206, 208, 210, the fabrication of the resonant circuit 200may be completed by mounting, soldering, or otherwise affixingcapacitive elements 220, 222 to the longitudinal ends 212, 214 of thearcuate inductive elements 208, 210 that span the air gaps 216, 218 andcapacitively couple the arcuate inductive elements 208, 210.

Referring now to FIGS. 1-2, in an exemplary embodiment, the resonantcircuitry 122 in the oscillator system 100 is realized as resonantcircuit 200 such that the annular resonance structure 202 is coupledbetween the output of the amplifier arrangement 120 and the input of theamplifier arrangement 120. In this regard, the input inductive element204 is electrically coupled to node 118 and the output inductive element206 is electrically coupled to node 112. For example, the amplifieroutput impedance matching circuitry 126 may include a microstrip formedon the electrical substrate 201 that is connected to or otherwiseintegral with the input inductive element 204 and the amplifier inputimpedance matching circuitry 124 may include a second microstrip that isconnected to or otherwise integral with the output inductive element206. The physical dimensions of the input inductive element 204 arechosen to match the input impedance of the resonant circuit 200 to theimpedance at node 118, and similarly, the physical dimensions of theoutput inductive element 206 are chosen to match the output impedance ofthe resonant circuit 200 to the impedance at node 112. In this regard,in an exemplary embodiment, the impedances of the impedance matchingcircuitry 124, 126 and the impedances of the inductive elements 204, 206and air gaps 224, 226 are cooperatively configured to provide a desiredgain for the oscillator arrangement 102 at the resonant frequency of theresonant circuitry 122, 200.

FIG. 3 depicts an exemplary embodiment of an adaptor 300 suitable foruse as the microwave adaptor 108 in the oscillator system 100 of FIG. 1.The adaptor 300 includes, without limitation, a plurality of coaxialportions 302, 304, 306, an antenna portion 308, and an input impedancematching portion 310. In an exemplary embodiment, the input impedancematching portion 310 includes an input segment 312 of microstrip oranother conductive material (e.g., a conductive metal trace) and aninput capacitive element 314 coupled between the input segment 312 and aground reference voltage node 316 (e.g., node 142), wherein the inputsegment 312 and the capacitive element 314 are configured to match theinput impedance at the input node 318 of the microwave adaptor 300 to anode having an oscillating electrical signal (e.g., output node 118)that is coupled to the input node 318 of the microwave adaptor 300. Forexample, as described in greater detail below in the context of FIG. 4,in accordance with one embodiment when the microwave adaptor 108 isrealized as adaptor 300, the capacitive element 314 is realized as acapacitor having a capacitance of about 2.2 picofarads and the inputsegment 312 is realized as a microstrip transmission line segment havinga length chosen to provide an impedance of 50 ohms at 2.45 GHz to matchthe 50 ohm output impedance of the oscillator arrangement 102 at theoutput node 118. At least the antenna portion 308 of the microwaveadaptor 300 is disposed within a waveguide (e.g., at or near the inputof waveguide 110) to radiate oscillating electromagnetic signals (orwaves) corresponding to input electrical signals received at the adaptorinput node 318 into the waveguide, as described in greater detail below.

The coaxial portions 302, 304, 306 are coupled electrically in seriesbetween the input impedance matching portion 310 and the antenna portion308 to translate the impedance at the adaptor input node 318 to theinput impedance of the waveguide (e.g., waveguide 110) where the lastcoaxial portion 306 is coupled to the antenna portion 308. In exemplaryembodiments, the coaxial portions 302, 304, 306 are substantiallycylindrical in shape, with each coaxial portion 302, 304, 306 includingan inner cylindrical segment of conductive material (or innerconductor), a dielectric material surrounding or otherwisecircumscribing the inner conductor, and an outer shielding materialsurrounding or otherwise circumscribing the dielectric material. Forexample, in an exemplary embodiment, the first coaxial portion 302includes an inner cylindrical segment 320 of copper or another suitableconductive material and a surrounding portion 322 of dielectricmaterial, such as Teflon, circumscribing the inner conductor 320. Inthis regard, the surrounding dielectric portion 322 may be substantiallycylindrical with a hollow interior bore (or opening) that corresponds tothe diameter and/or circumference of the inner conductor 320. The firstcoaxial portion 302 also includes an outer shielding segment 324 ofcopper or another conductive material that circumscribes at least aportion of the surrounding dielectric portion 322. As described ingreater detail below, the outer shielding segment 324 includes a flangeportion 356 that extends perpendicular to the longitudinal axis of theportion 302 to facilitate mounting and grounding the outer shieldingsegment 324. As illustrated, an end portion 326 of the inner conductor320 extends from the surrounding dielectric portion 322 and iselectrically connected to the input microstrip segment 312. Inaccordance with one embodiment, the length of the extension of the endportion 326 is greater than about 5 millimeters to facilitate theelectrical connection between the end portion 326 and the inputmicrostrip segment 312. For example, the end portion 326 may be realizedas a semi-circular cross-section of the inner conductor 320 (e.g., onehalf of the cylinder) that is soldered or otherwise affixed to the inputmicrostrip segment 312.

In the illustrated embodiment, the second coaxial portion 304 includesan inner cylindrical segment 328 of copper or another suitableconductive material that is electrically connected to the innerconductor 320 of the first coaxial portion 302, a surrounding portion330 of dielectric material, and an outer shielding segment 332 of aceramic material. In an exemplary embodiment, the inner conductor 328 ofthe second coaxial portion 304 is integral with and/or contiguous to theinner conductor 320 of the first coaxial portion 302, and thesurrounding dielectric portion 330 of the second coaxial portion 304 isintegral with and/or contiguous to the surrounding dielectric portion322 of the first coaxial portion 302. Similarly, the third coaxialportion 306 includes an inner cylindrical segment 334 of copper oranother suitable conductive material that is electrically connected tothe inner conductor 328 of the second coaxial portion 304, a surroundingportion 336 of dielectric material, and an outer shielding segment 338of copper or another conductive material, wherein the inner conductor334 of the third coaxial portion 306 is integral with and/or contiguousto the inner conductor 328 of the second coaxial portion 304 and thesurrounding dielectric portion 336 is integral with and/or contiguous tothe surrounding dielectric portion 330. Accordingly, the innerconductors 320, 328, 334 may be realized as a unitary, contiguous and/orintegral cylindrical segment of copper or another conductive materialhaving different diameters and/or lengths across the different coaxialportions, and; likewise, the surrounding dielectric portions 322, 330,336 may be realized as a unitary, contiguous and/or integral cylindricalsegment of Teflon or another dielectric material having differentdiameters and/or lengths across different coaxial portions, as describedin greater detail below. As illustrated in FIG. 3, the inner conductor334 and the outer shielding segment 338 of the third coaxial portion 306extend beyond the surrounding dielectric material 336 to provide asubstantially hollow region having the inner conductor 334 disposedtherein. As described in greater detail below, the antenna portion 308is realized as a conductive capping portion disposed within the hollowregion defined by the outer shielding segment 338 that electricallyconnects the inner conductor 334 to the outer shielding segment 338 tofacilitate radiation of electromagnetic waves (or signals) from theadaptor 300 into a waveguide, cavity, or the like. In an exemplaryembodiment, the outer shielding portions 326, 332, 338 correspond to amagnetron antenna head. To put it another way, the adaptor 300 may beformed by providing the inner conductors 320, 328, 334 and surroundingdielectric portions 322, 330, 336 within the magnetron antenna head andinserting the antenna portion 308 into the end of the magnetron antennahead.

In accordance with one or more exemplary embodiments, each coaxialportion 302, 304, 306 has a different impedance than the other coaxialportions 302, 304, 306. In the illustrated embodiment, each coaxialportion 302, 304, 306 has one or more diameters (or circumferences) thatis different from the corresponding diameters (or circumferences) of theother coaxial portions 302, 304, 306. For example, the diameter (orcircumference) of the inner conductor 320 of the first coaxial portion302 (illustrated by arrows 360) is greater than the diameter (orcircumference) of the inner conductors 328, 334 of the other coaxialportions 304, 306, and the nominal diameter (or circumference) of thesurrounding dielectric portion 322 of the first coaxial portion 302(illustrated by arrows 362) is greater than the diameter (orcircumference) of the surrounding dielectric portions 330, 336 of theother coaxial portions 304, 306. Likewise, while the inner conductors328, 334 of the second and third coaxial portions 304, 306 havesubstantially the same diameter (or circumference) (illustrated byarrows 366), the diameter (or circumference) of the surroundingdielectric portion 330 for the second coaxial portion 304 (illustratedby arrows 368) is greater than the diameter (or circumference) of thesurrounding dielectric portion 336 for the third coaxial portion 306(illustrated by arrows 372) and the diameter (or circumference) of theouter shielding portion 332 of the second coaxial portion 304 is greaterthan the diameter (or circumference) of the outer shielding portion 338of the third coaxial portion 306.

Still referring to FIG. 3, the antenna portion 308 is realized as aconductive capping portion disposed within the hollow region defined bythe extension of the outer shielding portion 338 that electricallyconnects the inner conductor 334 to the outer shielding portion 338,such that the inner conductor 334 to the outer shielding portion 338 areeffectively short-circuited together. The antenna portion 308 includes acylindrical portion 340 and a cap portion 342 that is integral with thecylindrical portion 340. In an exemplary embodiment, antenna portion 308includes a central bore 344 (or hole or opening) that extends throughthe cylindrical portion 340 and the cap portion 342 and has a diameter(or circumference) that is substantially equal to or otherwisecorresponds to the diameter (or circumference) of the inner conductor334, such that the portion of the inner conductor 334 that extends fromthe surrounding dielectric material 336 into the hollow region definedby the extension of the shielding portion 338 is disposed within thecylindrical portion 340 when the cylindrical portion 340 is insertedwithin the hollow region, as illustrated in FIG. 3. In this regard, thebore 344 conforms to or is otherwise flush with the inner conductor 334so that the extending portion of the inner conductor 334 contacts thecylindrical portion 340. The cylindrical portion 340 has a diameter (orouter circumference) that is substantially equal to or otherwisecorresponds to the inner circumference of the shielding portion 338 sothat the outer circumferential surface of the cylindrical portion 340contact the inner circumferential surface of the shielding portion 338.Thus, when the portions 340, 342 are realized as a conductive material,such as copper, the antenna portion 308 and/or cylindrical portion 340electrically connects the inner conductor 334 to the outer shieldingportion 338.

In an exemplary embodiment, the inner conductor 334 and the outershielding portion 338 each extend beyond the surrounding portion 336 bya first amount (illustrated by arrows 376) and the length of thecylindrical portion 340 is substantially equal to or otherwisecorresponds to that amount of extension, so that the cylindrical portion340 contacts the surrounding portion 336 when the cylindrical portion340 is inserted within the hollow region defined by the extendingportion of the outer shielding portion 338. Thus, there are no interiorair gaps or voids between the cylindrical portion 340 and the outershielding portion 338. In an exemplary embodiment, the cap portion 342has a diameter (or circumference) that is substantially equal to orotherwise corresponds to the outer diameter (or outer circumference) ofthe outer shielding portion 338. The cap portion 342 has a length(illustrated by arrows 378) such that the bore 344 provides an air gap346 at the longitudinal end of the extending portion of the innerconductor 334 that is aligned with, coaxial to and/or concentric withthe inner conductor 334. In accordance with one embodiment, the length378 of the cap portion 342 is greater than about 1 millimeter, andpreferably, around 1.5 millimeters. For example, as described above inthe context of FIG. 1, the antenna portion 308 and/or cylindricalportion 340 may be inserted into or otherwise disposed within awaveguide (e.g., waveguide 110) capable of directing electromagneticwaves radiating from the air gap 346 into a cavity (or cooking chamber)of a microwave oven (e.g., microwave oven 150). By virtue of theelectrical connection between the inner conductor 334 and the outershielding portion 338 provided by the antenna portion 308,electromagnetic waves corresponding to the oscillating electricalsignals propagating along the inner conductor 334 to radiate from theantenna portion 308 and the outer shielding portion 338 into thesurrounding medium.

In an exemplary embodiment, the microwave adaptor 300 is inserted withina substantially planar mounting structure 350 that is mounted orotherwise affixed to a waveguide (e.g., waveguide 110). In this regard,the mounting structure 350 includes an opening (or hole) aligned with aninput of the waveguide that allows a least a portion of the microwaveadaptor 300 to protrude through the mounting structure 350 into thewaveguide. In the illustrated embodiment of FIG. 3, the opening conformsto the outer diameter (or circumference) of the second coaxial portion304 and has a diameter (or circumference) that is less than the diameter(or circumference) of the first coaxial portion 302 so that only thesecond and third coaxial portions 304, 306 are capable of extendingthrough the mounting structure 350 into the waveguide. In accordancewith one or more embodiments, the mounting structure 350 is realized asa conductive material, such as iron or aluminum. In the illustratedembodiment, a first cylindrical mounting structure 352 having an opening(or hole) corresponding to the diameter (or outer circumference) of thefirst coaxial portion 302 is affixed or otherwise mounted to themounting structure 350. As illustrated, the length of the firstcylindrical mounting structure 352 corresponds to the length of theouter shielding portion 324. In an exemplary embodiment, the firstcylindrical mounting structure 352 is realized as aluminum or anotherconductive material that provides electrical connectivity between themounting structure 350 and the outer shielding portion 324, so that theouter shielding portion 324, the mounting structure 350, and the firstcylindrical mounting structure 352 have the same electrical potential(e.g., ground). A second cylindrical mounting structure 354 having alength substantially equal to the length of the segment of thesurrounding dielectric portion 322 that extends from the outer shieldingportion 324 and an opening (or hole) that corresponds to or otherwiseconforms to the outer surface of the segment of the surroundingdielectric portion 322 that extends from the outer shielding portion 324is affixed or otherwise mounted to the first cylindrical mountingstructure 352. In an exemplary embodiment, the second cylindricalmounting structure 354 is realized as a brass material or anotherconductive material. The flange portion 356 of the outer shieldingsegment 324 contacts the cylindrical mounting structures 352, 354 toprovide an electrical connection that grounds the second cylindricalmounting structure 354 to the electrical potential of the firstcylindrical mounting structure 352. Although not illustrated in FIG. 3,in some embodiments, one or more washers (or spacers) may be disposedbetween the cylindrical mounting structures 352, 354 to maintain thespacing between the cylindrical mounting structures 352, 354 and protectthe flange portion 356. In this regard, the washer may circumscribe theflange portion 356 or have a diameter that is less than the diameter ofthe flange portion 356 to circumscribe the dielectric portion 322between the flange portion 356 and the second cylindrical mountingstructure 354. The washer may be realized as a brass material or anotherconductive material. By virtue of the conductivity of the mountingstructures 350, 352, 354 and the flange portion 356, the outer shieldingportion 324 of the adaptor 300 may be grounded when the adaptor 300 ismounted to a waveguide (e.g., to the same electrical potential as theexterior of the waveguide via mounting structure 350).

FIG. 4 illustrates an equivalent circuit for one exemplary embodiment ofthe microwave adaptor 300 illustrated in FIG. 4 suitable for use in theoscillator system 100 of FIG. 1. In accordance with one embodiment, theinput microstrip segment 312 is configured to provide impedance of about50 ohms at 2.45 GHz and the capacitive element 314 provides acapacitance of about 2.2 picofarads to match the impedance of themicrowave adaptor 300 to the impedance at the output node 118 of theoscillator arrangement 102. For the embodiment depicted by FIG. 4, theinner conductor 320 of the first coaxial portion 302 has a diameter(illustrated by arrows 360) of about 3.35 millimeters (0.132 inches),the surrounding portion 322 has a nominal diameter (illustrated byarrows 362) of about 0.1473 meters (0.580 inches), and the innerconductor 320 and the surrounding dielectric portion 322 each have alength (illustrated by arrows 364) of about 0.1789 meters (0.704 inches)to provide an impedance of about 61.2 ohms at 2.45 GHz. As illustratedin FIG. 3, in one embodiment, the surrounding dielectric portion 322 andthe outer shielding portion 324 are chamfered at an angle of about 75°(relative to the plane of the planar mounting structure 350) to/from thelocation where the first cylindrical mounting structure 352 interfaceswith the second cylindrical mounting structure 354, and the surroundingdielectric portion 322 is chamfered at an angle of 62° (relative to theplane of the planar mounting structure 350) near the interface with thesecond coaxial portion 304. For the second coaxial portion 304, theinner conductor 328 has a diameter (illustrated by arrows 366) of about1 millimeter (0.04 inches), the surrounding portion 330 has a nominaldiameter (illustrated by arrows 368) of about 0.1070 meters (0.421inches), and the inner conductor 328 and the surrounding dielectricportion 330 each have a length (illustrated by arrows 370) of about0.1488 meters (0.586 inches) to provide an impedance of about 98.5 ohmsat 2.45 GHz. As illustrated in FIG. 3, in one embodiment, thesurrounding dielectric portion 330 is chamfered at an angle of 56°(relative to the plane of the planar mounting structure 350) near theinterface with the third coaxial portion 306. For the third coaxialportion 306, the inner conductor 334 has the same diameter 366 as theinner conductor 328, the surrounding portion 336 has a diameter(illustrated by arrows 372) of about 0.0660 meters (0.260 inches), andthe surrounding dielectric portion 336 has a length (illustrated byarrows 374) of about 0.1524 meters (0.600 inches) to provide animpedance of about 79 ohms at 2.45 GHz. Thus, for the embodiment of FIG.4, the microwave adaptor 300 translates the oscillating electricalsignals at the adaptor input node 318 (e.g., output node 118) from a 50ohm impedance to an impedance of about 288.7 ohms at 2.45 GHz at theinput of the waveguide 110. In an exemplary embodiment, the length ofthe extending portions of the inner conductor 224 and the outershielding portion 338 (illustrated by arrows 376) is about 6.1millimeters (0.124 inches) and the length of the cap portion 342(illustrated by arrows 378) is about 1.52 millimeters (0.06 inches).

Referring now to FIGS. 1-4, one advantage of the oscillator systemsdescribed above is that the oscillator systems are capable of producingmicrowave signals having an equivalent output power to those produced byconventional magnetrons at a lower voltage and without the use of amagnetron. In this regard, in lieu of a magnetron antenna used totransfer microwave signals from the magnetron to a waveguide and/orcavity, the microwave adaptor 108 translates the impedance of theoscillating electrical signals generated by the oscillator arrangement102 from approximately 50 ohms at the output node 118 of the oscillatorarrangement 102 to the input impedance of the waveguide 110 (e.g.,approximately 300 ohms) and includes an antenna portion inserted withinthe waveguide 110 to radiate electromagnetic waves into the waveguide110. In this regard, by matching the input impedance of the microwaveadaptor 108 to the output impedance of the oscillator arrangement 102,the power transfer from the oscillator arrangement 102 to the microwaveadaptor 108 is improved, and by matching the output impedance of themicrowave adaptor 108 to the input impedance of the waveguide 110, theforward transmission of the electromagnetic waves radiated by themicrowave adaptor 108 is improved.

For the sake of brevity, conventional techniques related to resonators,amplifiers, biasing, load modulation, impedance matching, microwaveapplications, and other functional aspects of the systems (and theindividual operating components of the systems) may not be described indetail herein. Furthermore, the connecting lines shown in the variousfigures contained herein are intended to represent exemplary functionalrelationships and/or physical couplings between the various elements. Itshould be noted that many alternative or additional functionalrelationships or physical connections may be present in an embodiment ofthe subject matter. In addition, certain terminology may also be usedherein for the purpose of reference only, and thus are not intended tobe limiting, and the terms “first”, “second” and other such numericalterms referring to structures do not imply a sequence or order unlessclearly indicated by the context.

As used herein, a “node” means any internal or external reference point,connection point, junction, signal line, conductive element, or thelike, at which a given signal, logic level, voltage, data pattern,current, or quantity is present. Furthermore, two or more nodes may berealized by one physical element (and two or more signals can bemultiplexed, modulated, or otherwise distinguished even though receivedor output at a common node).

The foregoing description refers to elements or nodes or features being“connected” or “coupled” together. As used herein, unless expresslystated otherwise, “connected” means that one element is directly joinedto (or directly communicates with) another element, and not necessarilymechanically. Likewise, unless expressly stated otherwise, “coupled”means that one element is directly or indirectly joined to (or directlyor indirectly communicates with) another element, and not necessarilymechanically. Thus, although the schematic shown in the figures depictone exemplary arrangement of elements, additional intervening elements,devices, features, or components may be present in an embodiment of thedepicted subject matter.

In conclusion, an exemplary embodiment of an adaptor is provided. Theadaptor comprises an input segment of a conductive material, a firstcoaxial portion including a first inner conductor coupled to the inputsegment and a first outer shielding segment, and a capping portioncoupled to the first coaxial portion to electrically couple the firstinner conductor and the first outer shielding segment. In oneembodiment, the capping portion includes an air gap aligned with an endof the first inner conductor. In another embodiment, the adaptor furthercomprises a second coaxial portion including a second inner conductorcoupled between the input segment and the first inner conductor, whereina diameter of the second coaxial portion is different from a diameter ofthe first coaxial portion. In yet another embodiment, the adaptorfurther comprises a second coaxial portion including a second innerconductor coupled between the input segment and the first innerconductor, wherein an impedance of the second coaxial portion isdifferent from an impedance of the first coaxial portion. In accordancewith another embodiment, the adaptor further comprises a capacitiveelement coupled between the input segment and a reference voltage node.In one embodiment, the input segment comprises a microstrip transmissionline.

In accordance with another exemplary embodiment, an adaptor is providedthat comprises a first coaxial portion having a first diameter, a secondcoaxial portion having a second diameter, wherein the second diameter isdifferent from the first diameter, the second coaxial portion includingan inner conductive portion and an outer shielding segment, and acapping portion coupled to the second coaxial portion to electricallycouple the inner conductive portion and the outer shielding segment. Inone embodiment, the adaptor further comprises a segment of conductivematerial coupled to the first coaxial portion and a capacitive elementcoupled between the segment of conductive material and a referencevoltage node. In a further embodiment, the first diameter is greaterthan the second diameter. In another embodiment, the segment isconnected to an inner conductive portion of the first coaxial portion.In accordance with one embodiment, the inner conductive portion of thesecond coaxial portion has the second diameter, wherein the firstcoaxial portion includes a second inner conductive portion having thefirst diameter. In yet another embodiment, the first coaxial portionincludes a second inner conductive portion and a first dielectricportion surrounding the second inner conductive portion, the firstdielectric portion has the first diameter, the second coaxial portionincludes a second dielectric portion surrounding the inner conductiveportion, and the second dielectric portion has the second diameter. Inone embodiment, the first diameter is greater than the second diameter.In accordance with yet another embodiment, the capping portion includesan opening aligned with the inner conductive portion to provide an airgap at an end of the inner conductive portion. In a further embodiment,the outer shielding segment defines a hollow region having an extendingportion of the inner conductive portion disposed therein, the cappingportion includes a cylindrical portion of conductive material disposedwithin the hollow region, the extending portion of the inner conductiveportion is disposed within the opening in the cylindrical portion, andthe cylindrical portion contacts the inner conductive portion and theouter shielding segment. In accordance with another embodiment, animpedance of the first coaxial portion is different from an impedance ofthe second coaxial portion.

In accordance with another embodiment, an oscillator system is provided.The oscillator system comprises a waveguide having an input impedance,an oscillator arrangement to generate an oscillating signal at a firstnode, and an adaptor coupled to the first node. The adaptor comprises aninput segment of conductive material coupled to the first node, anantenna portion disposed within the waveguide, and one or more coaxialportions coupled between the antenna portion and the input segment totranslate the oscillating signal to the input impedance of the waveguideat the antenna portion. In one embodiment, the oscillator system furthercomprises a capacitive element coupled between the input segment and areference voltage node, wherein an impedance of the input segmentcorresponds to an output impedance at the first node and the one or morecoaxial portions are configured to translate the oscillating signal fromthe output impedance to the input impedance of the waveguide. In anotherembodiment, the one or more coaxial portions comprise a first coaxialportion having a first inner conductor coupled to the input segment anda second coaxial portion having a second inner conductor coupled to thefirst inner conductor, wherein a diameter of the first inner conductoris different from a diameter of the second inner conductor. In yetanother embodiment, the oscillator arrangement comprises a firstamplifier having a first amplifier input and a first amplifier outputcoupled to the first node, and an annular resonance structure coupledbetween the first amplifier output and the first amplifier input.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexemplary embodiment or embodiments described herein are not intended tolimit the scope, applicability, or configuration of the claimed subjectmatter in any way. Rather, the foregoing detailed description willprovide those skilled in the art with a convenient road map forimplementing the described embodiment or embodiments. It should beunderstood that various changes can be made in the function andarrangement of elements without departing from the scope defined by theclaims, which includes known equivalents and foreseeable equivalents atthe time of filing this patent application. Accordingly, details of theexemplary embodiments or other limitations described above should not beread into the claims absent a clear intention to the contrary.

1. An adaptor, comprising: an input segment of a conductive material; afirst coaxial portion including a first inner conductor coupled to theinput segment and a first outer shielding segment; and a capping portioncoupled to the first coaxial portion to electrically couple the firstinner conductor and the first outer shielding segment.
 2. The adaptor ofclaim 1, wherein the capping portion includes an air gap aligned with anend of the first inner conductor.
 3. The adaptor of claim 1, furthercomprising a second coaxial portion including a second inner conductorcoupled between the input segment and the first inner conductor, whereina diameter of the second coaxial portion is different from a diameter ofthe first coaxial portion.
 4. The adaptor of claim 1, further comprisinga second coaxial portion including a second inner conductor coupledbetween the input segment and the first inner conductor, wherein animpedance of the second coaxial portion is different from an impedanceof the first coaxial portion.
 5. The adaptor of claim 1, furthercomprising a capacitive element coupled between the input segment and areference voltage node.
 6. The adaptor of claim 1, wherein the inputsegment comprises a microstrip transmission line.
 7. An adaptor,comprising: a first coaxial portion having a first diameter; a secondcoaxial portion having a second diameter, wherein the second diameter isdifferent from the first diameter, the second coaxial portion includingan inner conductive portion and an outer shielding segment; and acapping portion coupled to the second coaxial portion to electricallycouple the inner conductive portion and the outer shielding segment. 8.The adaptor of claim 7, further comprising: a segment of conductivematerial coupled to the first coaxial portion; and a capacitive elementcoupled between the segment of conductive material and a referencevoltage node.
 9. The adaptor of claim 8, wherein the first diameter isgreater than the second diameter.
 10. The adaptor of claim 8, whereinthe segment is connected to an inner conductive portion of the firstcoaxial portion.
 11. The adaptor of claim 7, the inner conductiveportion of the second coaxial portion having the second diameter,wherein the first coaxial portion includes a second inner conductiveportion having the first diameter.
 12. The adaptor of claim 7, wherein:the first coaxial portion includes a second inner conductive portion anda first dielectric portion surrounding the second inner conductiveportion; the first dielectric portion has the first diameter; the secondcoaxial portion includes a second dielectric portion surrounding theinner conductive portion; and the second dielectric portion has thesecond diameter.
 13. The adaptor of claim 12, wherein the first diameteris greater than the second diameter.
 14. The adaptor of claim 7, whereinthe capping portion includes an opening aligned with the innerconductive portion to provide an air gap at an end of the innerconductive portion.
 15. The adaptor of claim 14, wherein: the outershielding segment defines a hollow region having an extending portion ofthe inner conductive portion disposed therein; the capping portionincludes a cylindrical portion of conductive material disposed withinthe hollow region; the extending portion of the inner conductive portionis disposed within the opening in the cylindrical portion; and thecylindrical portion contacts the inner conductive portion and the outershielding segment.
 16. The adaptor of claim 7, wherein an impedance ofthe first coaxial portion is different from an impedance of the secondcoaxial portion.
 17. An oscillator system, comprising: a waveguidehaving an input impedance; an oscillator arrangement to generate anoscillating signal at a first node; and an adaptor coupled to the firstnode, the adaptor comprising: an input segment of conductive materialcoupled to the first node; an antenna portion disposed within thewaveguide; and one or more coaxial portions coupled between the antennaportion and the input segment to translate the oscillating signal to theinput impedance of the waveguide at the antenna portion.
 18. Theoscillator system of claim 17, further comprising a capacitive elementcoupled between the input segment and a reference voltage node, wherein:an impedance of the input segment corresponds to an output impedance atthe first node; and the one or more coaxial portions are configured totranslate the oscillating signal from the output impedance to the inputimpedance of the waveguide.
 19. The oscillator system of claim 17,wherein the one or more coaxial portions comprise: a first coaxialportion having a first inner conductor coupled to the input segment; anda second coaxial portion having a second inner conductor coupled to thefirst inner conductor, wherein a diameter of the first inner conductoris different from a diameter of the second inner conductor.
 20. Theoscillator system of claim 17, wherein the oscillator arrangementcomprises: a first amplifier having a first amplifier input and a firstamplifier output coupled to the first node; and an annular resonancestructure coupled between the first amplifier output and the firstamplifier input.